1. Field of the Invention
This invention relates to exhaust gas oxygen sensor fault monitoring for an internal combustion engine of a motor vehicle.
2. Related Art
As emissions requirements become more stringent, it becomes more important to ensure that sensors that are used in the control of an internal combustion engine are working correctly. In the case of an oxygen sensor, for example a universal heated exhaust gas oxygen (UHEGO) sensor as used in an exhaust system of an internal combustion engine, a diagnostic monitor is typically provided to check for a potentially slow response of the oxygen sensor as indicative of a sensor fault. An example of such a diagnostic monitor can operate by monitoring the average sensor output against an average air-fuel ratio (AFR) control feedback amplitude over a set period of time and by applying a forced fuel dither to the normal AFR control to check for a slow oxygen sensor response.
However, it is also important to ensure that such monitoring accurately reflects the true performance of the oxygen sensor, for example to avoid, wherever possible, false reporting of apparent sensor faults when the sensor is in fact operating correctly.
An aim of the present invention is to reduce potential false reporting of potential sensor malfunctions.